In various pyrometallurgical processes, attention has centered of later upon the use of a cyclone chamber into which the fine-grained solids, high-oxygen gases and, if desired, an energy carrier such as a fuel are introduced to undergo reaction.
Cyclones of this type have found application in combustion installations, e.g. furnaces, as well as in pyrometallurgy: Various systems using such cyclones are described in the following publications: Lexikon der Technik, vol. 7, Lexikon der Energietechnik und Kraftmaschinen, L - Z, Deutsche Verlagsanstalt Stuttgart, 1965; I. A. Onajew, Zyklonschmelzen von Kupfer und polymetallischen Konzentraten, Neue Hutte 10, 1965, pp. 210 et seq.; Printed German Applications (Auslegeschrift) 11 61 033, 19 07 204, and 20 10 872; Opened German Specification (Offenlegungsschrift) 21 09 350; Sch. Tschokin, Freiburger Forschungshefte, B150, Leipzig, 1969, pp. 41 et seq.; G. Melcher et al and E. Muller in Erzmetall, vol. 28, 1975, pp. 313 et seq., vol. 29, 1976, pp. 322 et seq., vol. 30, 1977, pp. 54 et seq
The reason why cyclone chambers have been found to be especially effective in pyrometallurgical treatments, and, more generally for carrying out reactions in which an oxygen-containing gas participates, is that the throughput of the cyclone per unit of reactor volume is high compared to other solid/gas treatment systems. High reaction temperatures can be obtained, thereby permitting volatilization of various components of the solid feed.
There is described in Printed German Application (Auslegeschrift) No. 22,53,074 and corresponding to U.S. Pat. No. 3,915,692, a technique which utilizes a cyclone chamber and which ensures that the reactants are intensely mixed and are caused to react to a considerable extent in a vertical combustion path before entering the cyclone chamber. This system provides a vertical combustion path at the inlet of the cyclone chamber.
The advantage of this system, over the operation of a cyclone chamber without a combustion path ahead of the chamber is that it precludes a separation of particles of the feed solid in the cyclone chamber and the entrapment of the separated solids in the molten film which lines the walls of the cyclone chamber and which might prevent these particles from participating in the reaction.
While the aforedescribed system permits cyclone reactors to be used most effectively for the reaction of metallurgical particulates with high-oxygen gases, it is of interest in many cases to carry out further reaction in the gas phase. For example, the gas phase obtained in a given process may contain, just as does a molten phase, a substance which is only an intermediate and which desirably should undergo a further reaction with a substance not normally present in either the gas phase or the molten phase. As a result, it is necessary to recover the gas phase and carry out a reaction between the intermediate or unreacted substance therein and a further reaction. In many instances, the unreacted substance of the gas phase must be separated from other components of the gas phase so as to carry the further reaction in an efficaceous manner. Naturally this leads to additional capital expenditures for separating apparatus and further reactants and presents complications with respect to separation and subsequent reaction. From a point of view of energy economy, moreover, systems of this type are disadvantageous because the gas phase may have been reheated to permit the subsequent reactions to be carried out. All in all, therefore, prior cyclone reaction processes, including that of the most advanced systems described in U.S. Pat. No. 3,915,692, may not be fully satisfactory for all purposes.